Truly understand the threshold for document set in document library in SharePoint

Recently, I am working on an issue with threshold. The problem is that when the user navigates to a view of the document library, it displays the error message “list view threshold is exceeded”. However, in the view, it has no data. The list view threshold limit is 5000 by default for the non-admin user. This limit is not the number of items returned by your query; it is the total number of items the database needs to read to calculate the returned result set. So although the view does not return any result but to calculate the result (no data to show), it needs to access more than 5000 items in the database. To fix the issue, you need to create an index for the column that you use in the filter for the view. Let’s look at the problem in details. You can download a solution to replicate this issue here.